EXCAVATING THE RAW MATERIALS. 381 



The costs above cited show the cheapness with which marl and clay 

 can be excavated. The total costs of raw material at a wet-process 

 plant may therefore range from 3 to 6 cents per barrel of cement. 



References on quarrying, etc. The following books and papers 

 contain data of interest on methods and costs of quarrying, etc. 



Crane, W. A. Shale Mine at La Harpe, Kansas. Mines and Minerals, Dec., 

 1902, pp. 217-218. 



De Kalb, C. Manual of Explosives. 16mo, 126 pp. Ontario Bureau of Mines, 

 1900. 



Foster. C. Le Neol. Elements of Mining and Quarrying. 12mo, 321 pp. 1903. 



Gillette, H. P. Earthwork and Its Cost. 12mo, 244 pp. New York, 1903. 



Gillette, H. P. Rock Excavation: Methods and Cost. 12mo, 376 pp. New 

 York, 1904. 



Green, N. M. [Cost of raw materials in cement manufacture.] Engineering 

 Record, Jan. 23, 1904. 



Guttmann, O. Blasting. 8vo, 179 pp. London, 1892. 



Harris, E. G. The Harris System of Pumping with Compressed Air. Mines 

 and Minerals, vol. 25, pp. 513-514, May, 1905. 



Knight, W. B. Quarrying Limestone at ,Rockland, Maine. Mines and Min- 

 erals, August, 1899. 



